A plane crosses the Atlantic Ocean (3000 miles) with an airspeed of 500 miles per hour. The cost C in dollars) per passenger is given by
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C(x) = 50 + = +
9 х
where x is the ground speed (airspeed wind).
(a) What is the cost when the ground speed is 350 miles per hour, 460 miles per hour?
(b) Find the domain of C.
(c) Use a graphing calculator to graph the function C = C(x).
(d) Create a TABLE with TbiStart = 0 and ATbl = 50.
(e) To the nearest 50 miles per hour, what ground speed minimizes the cost per passenger?

true? is that what you're asking or do you mean something else?

solution:

the given function is ,

      =

the three roots of this quadratic function is , 0 ,8 and 10.all the roots are real and rational.

if a quadratic equation is of the form ,

sum of the roots = a + b +c= 0+8+10=18=  

product of roots taken two at a time = a b + b c+ c a = 0+80+0=80 =  

product of roots = a b c = 0=  

there are 11 doors in a hall starting from 0 to 11.the entry in the hall is permitted through gate number 0 and exit is allowed through only gate number 8 and 10.so, three roots(0,8,10) of quadratic function is given by entry and exit route of this hall.